Segmented models for stress-strain diagrams

Tension and compression stress-strain data from tests of wood specimens were mathematically described by 2- or 3-segment models, respectively. Three or four parameters are required by the segmented models, but these are easily obtained from regression analysis of the digitized data. One required parameter is Young's modulus. The model parameters varied with moisture content, and it was possible to regenerate typical stress-strain diagrams at a variety of moisture levels for use in a finite-element program. This form of analysis makes it possible to demonstrate statistically that wood stress-strain diagrams have an initial linear segment, and that the stress-strain diagrams are not entirely curvilinear as some have proposed.